The primary aim of this study is to determine the relationship between the activity of single cortical neurons and two evoked cortical waveforms, the M-wave and the CNV, which qre themselves related to learned behavior. The M-wave is a short-duration, surface-negative waveform evoked by tone cues signalling the availability of a food reward if the subject, a squirrel monkey, bar-presses. The CNV, a longer-latency surface-negative wave-form, originally recorded in human subjects and now observed in squirrel monkeys, develops in and is sustained for the interval (thpically 1 sec) between a pair of cues, the second of which requires a response. Both waveforms are absent in untrained animals, and both are larger when the animal's interest in the reward, or in its acquisition, is greater. Largely on empiric grounds, the CNV is being used by audiologists, neurologists, and psychiatrists as a diagnostic tool. Little is known about the neurophysiological mechanisms of generation of either waveform, although evidence indicates that both are generated locally in cortex by neuronal mechanisms. Neither has been investigated at the unitary level and neither has been investigated extensively by a laminar analysis to determine the level in cortex at which they are generated. These are the primary goals of the proposed work.